• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.240-253
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• 2017

Latin hypercube sampling is widely used design-of-experiment technique to select design points for simulation which are then used to construct a surrogate model. The exploration/exploitation properties of surrogate models depend on the size and distribution of design points in the chosen design space. The present study aimed at evaluating the performance characteristics of various surrogate models depending on the Latin hypercube sampling (LHS) procedure (sample size and spatial distribution) for a diverse set of optimization problems. The analysis was carried out for two types of problems: (1) thermal-fluid design problems (optimizations of convergent-divergent micromixer coupled with pulsatile flow and boot-shaped ribs), and (2) analytical test functions (six-hump camel back, Branin-Hoo, Hartman 3, and Hartman 6 functions). The three surrogate models, namely, response surface approximation, Kriging, and radial basis neural networks were tested. The important findings are illustrated using Box-plots. The surrogate models were analyzed in terms of global exploration (accuracy over the domain space) and local exploitation (ease of finding the global optimum point). Radial basis neural networks showed the best overall performance in global exploration characteristics as well as tendency to find the approximate optimal solution for the majority of tested problems. To build a surrogate model, it is recommended to use an initial sample size equal to 15 times the number of design variables. The study will provide useful guidelines on the effect of initial sample size and distribution on surrogate construction and subsequent optimization using LHS sampling plan.

• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.499-508
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• 2015

The purpose of this paper is to examine the structural relationship between experience(4Es), customer commitment and behavioral intention based on experience of the theme park as a hedonic destination. To carry out this study objective, a survey targeted for theme park customers was conducted from May 10. 2014 to June 10. 2014. These data were processed using SPSS 18.0 and Structural Equation Modeling with Amos 18.0 to test proposed hypotheses. The results are summarized as followed. First, the decomposition of path analysis revealed significant positive effects on customer commitment by entertainment experience, education experience, esthetic experience. and escape experience. While, entertainment experience was shown to have the largest influence on customer commitment. Second, customer commitment had a positive effect on revisit intention and WOM. Third, experiences have an indirect influence on revisit intention and WOM through the mediation of commitment. From the findings, the theme park is necessary to plan and develop experience program for more variable and special.

• Journal of Preventive Medicine and Public Health
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• v.37 no.4
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• pp.312-320
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• 2004

Objectives : An outbreak of acute hemorrhagic conjunctivitis (AHC) caused by coxsackie A24 (CA24) virus occurred in South Korea in 2002. CA24 was isolated for the first time from patients with AHC. Therefore, this study was conducted to understand the transmission routes and prevent another AHC outbreaks. Methods : The authors conducted a questionnaire survey among 1,730 students from 2 middle schools and 1 technical high school in Gyeongju city. For statistical analysis the chi-square test was used, and chi-square for trend method showing a level of significance less than p<0.05 was proven to be significant. Variables which were proven to be significant in univariate analysis were analysed by multiple logistic regression. Results : The attack rate was 57.1%. The student groups with rubbing one s own eyes, computer usage, and sharing cellular phone had a significantly higher AHC attack rate (p<0.05). According to the multiple logistic regression, the odds ratios for male, high school, computer use, sharing cellular phone, and rubbing one s own eyes were significant (p<0.05). Conclusion : The most significant feature of this outbreak was that many students rubbed their own eyes following contact with AHC patients in a deliberate attempt to avoid going to school. Other transmission methods were computer usage and sharing cellular phone. In the future, health and school authorities must plan new strategies for the prevention of AHC.

• Journal of Wetlands Research
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• v.14 no.2
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• pp.181-192
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• 2012

Dae Dong Stream basin has been selected and operated as a representative experimental basin of UNESCO IHP since year 2007. It is located at Daejeon Metropolitan city, Korea and hydrologic data such as precipitation, runoff, and water quality have been being collected and provided after establishing the monitoring plan as an experimental basin for city/disaster prevention. In this study, runoff characteristics for non-point sources of rainfall-runoff process from urban stream basins were analyzed using the flow and water quality data measured during the year 2011. As an operation result for the test subjected basin, rating curves at Panam Bridge and at Chulgap Bridge were prepared, and to compare runoff characteristics of non-point source by precipitation, by estimating the Event Mean Concentration(EMC) for 10 water quality items, runoff characteristics of non-point source per different observation points as per the precipitation, antecedent rainfall, and land utilization status were analyzed.

• Journal of Korean Physical Therapy Science
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• v.9 no.1
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• pp.25-36
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• 2002

Objectives: This study was conducted to find out risk factors related to elderly hip fracture, so that the result could provide basic data to establish prevention programs for hip fracture among the elderly. Methods: The data were collected from 199 cases hospitalized in 4 university hospitals in Pusan from January, 1996 to December, 1998, 193 healthy controls who visited elderly facilities in Pusan. The data were obtained from medical records and by using questionnaires through telephone contact or direct personal interview with the subjects or their family, and were analyzed for 2-test and multiple logistic regression. The risk factors were shown with odds ratios and their 95% confidence intervals. Results: In univariate analysis, the odds ratio of hip fracture risk was estimated to be 1.9 for the elderly aged 75 years as compare with those aging less than 65 years; 42 for those with job as compared with those without job; 3.3 for those with more than 6 children as compared with those with one or two children. For the variables related to physical characteristics, small height (p=0.015), light weight (p=0.000), and low BMI (p=0.014) were risk factors for elderly hip fracture. Sane variables related to health, such as previous history of illness (OR=3.3.), abnormal blood pressure (OR=1.6), previous fracture history (OR=22), lower limbs weakness (OR=12.1) and gait disturbance (OR=42.6), were significantly associated with the risk of hip fracture. In multiple logistic regression, risk factors for hip fracture were age, having job, lower limb weakness and previous history of illness. The adjusted odds ratios of hip fracture risk among the elderly were age (OR=1.1), having jobs (OR=11.7), weak lower limb (OR=10.8) and previous history of illnesses (OR=3.3), respectively. Conclusion: This study suggests that the plan for improving the daily living environment for the elderly systematically should be implemented to avoid the chances of fall, and that programs encouraging to practice regular exercise for physical activity and to promote health of the elderly should be developed.

• Journal of Korean Physical Therapy Science
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• v.9 no.1
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• pp.53-59
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• 2002

This study is research for effect of the involved lower limb weight bearing training on symmetrical weight supporting rate improvement by practicing involved lower limb weight bearing training of three weeks period to improve standing equilibrium problem with asymmetric weight supporting rate of hemiplegia. In result of the study, it has shown that P-value incase of involved supporting rate is lower than level of significance $\alpha$<.05 and mean improvement rate of experienced group is higher in comparison with controlled group and experienced group. In changing quantity of involved maximum supporting rate, P-value is .26 and higher than level of significance $\alpha$<.05, and so it did not show significant difference statistically. But in case of experienced group between pre and post-test, involved side supporting rate and involved side maximum supporting rate showed significant improvement in all. In comparison of relative characteristic training effect difference, it was shown that train-learning effect on case of 40-60 years old, hemorrhagic patient and standard body bun of patient is valuable, which showed significant improvement in case of paralytic side and disease period, it did not show significant difference on excercise learning effect in two above cases. In the above result, we can say that continuous weight bearing training on the involved lower limb for three weeks period help improve the involved side supporting rate of hemiplegia. Accordingly, the weight bearing training on the involved lower limb is training method that patient can easily train with simple guidance of therapists, without being special expensive equipment. Furthermore it can be helpful to establish home therapeutic plan for hemiplegia through education of a patron.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5115-5122
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• 2013

This paper has studied about the development and application of landslide collapse prediction real-time monitoring system based on USN to detect and measure the collapse of landslide. The rainfall measuring sensor, gap water pressure sensor, indicator displacement measuring sensor, index inclination sensor, water content sensor and image analysis sensor are selected and these are applied on the test bed. Each sensor's operation and performance for reliability verification is tested by the instrument which is installed in the field. As the result, u-IT based real-time landslide monitoring system which is developed by this research for landslide collapse detection could minimize life and property damages because it makes advance evacuation with collapse risk pre-estimate through real-time monitoring on roadside cut and bedrock slopes. This system is based on the results of this study demonstrate the effect escarpment plan are spread throughout.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.1
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• pp.44-51
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• 2005

To provide more accurate and reliable positioning and timing services to Korean nationwide users, the Ministry of Maritime Affairs and Fisheries of Korea is implementing Korean NDGPS (Nationwide DGPS), which is operational partly. And it also has a plan to construct WADGPS (Wide Area Differential GPS) system using sites and equipments of the NDGPS reference stations. For that, Seoul National University GNSS Laboratory is implementing and testing prototypes of WRS (Wide-area Reference Station) and WMS (Wide-area Master Station). Until now, because there are not enough installed WRSs to be used for computing wide area correction information, we cannot test algorithms of WMS with the data processed actually in WRSs. Therefore to evaluate the performance of the algorithms, we made a MATLAB program which can process RINEX (Receiver INdependent Exchange) format data with WADGPS algorithm. Using that program which consists of WRS, WMS and USER modules, we processed the data collected at NDGPS reference stations, which are saved in RINEX format. In WRS module, we eliminate the atmospheric delay error from the pseudorange measurement, smooth the measurement by hatch filter and calculate pseudorange corrections for each satellite. WMS module collects the processed data from each reference stations to generate the wide area correction information including estimated satellite ephemeris errors, ionospheric delays at each grid point, UDRE (User Differential Range Error), GIVE (Grid Ionosphere Vertical Error) and so on. In USER part, we use the measurements of reference stations as those of users and estimate the corrected users' positions and protection levels (HPL, VPL). With the results of estimation, we analyzed the performance of the algorithms. We assured the estimated UDRE /GIVE values and the protection levels bound the corresponding errors effectively. In this research, we can expect the possible performance of WADGPS in Korea, and the developed modules will be useful to implementation and improvement of the algorithms.

• School Mathematics
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• v.1 no.2
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• pp.637-660
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• 1999

Although ‘to understand mathematics’ is an important educational purpose, most student do not have a relational understanding of the basic concept of mathematics but have a instrumental understanding. This paper will investigate the possibility of using computers for enhancing relational understanding. In the ‘Qualitative case study’, three students who are in the first grade at E-High school took part in 7 activities during four weeks, and were later interviewed and engaged in informal discussion and were observed. This is the result of this study. 1. The three students were passive participants in mathematics problem solving situation at school. Therefore, student B just applied formulas which she had memorized, and student C would forgot the formulas occasionally. These common students needed to participate actively in doing mathematics. 2. The activities utilized two software healing with connection between graphs and function, giving the students the opportunity to plan, practice, and test by themselves. As a result, they understood the mathematical formulas and rules more deeply through their own trial and error, and then they gained thinking abilities necessary for doing mathematics. In addition, the activities boosted their confidence. 3. The understanding type of students was slightly different. Student A who received a high score, understood the most relationally, but student B who received a very high score, understood instrumentally and so couldn't app1y her knowledge to solving problems related to function concept. Student C who received a middle score lacked knowledge of mathematics but thought more creatively. The result is that students need an opportunity to think rotationally regardless of score. Therefore, this study concludes that using computer software will provide a positive effect for relational understanding in loaming function concept.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.3
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• pp.13-21
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• 2009

Digital map should have the up-to-dateness as well as the accuracy to perform a role as the national spatial data. As digital mapping process require aerial photograph, surveying, and field working, it consumes a lot of time and cost. So there is a limit to maintain the up-to-dateness. If we updates the digital map frequently by using the as-built drawings, we can prevent the waste of national budget by reuse of existing drawings and make accuracy updates from existing survey results. In spite of this advantages, due to insufficiency of CAD drawing standard, inconsistency of file types of as-built drawings and digital maps, and topology relations between input features and original features, so the frequent updates using the as-built drawings is on the difficult situation to perform. In this research, first, CAD features extracted from as-built drawings land the new/update whether original features exist or not and generate topology from spatial relation of features. Second, suggest the efficient partial-update-plan performing integrity test. As a result, guarantee the accuracy and the up-to-dateness of digital map.